Lubricating Oil Composition

ABSTRACT

A lubricating oil composition including at least one sulphurized overbased metal phenate detergent prepared from a C 9 -C 15  alkyl phenol, at least one sulphurizing agent, at least one metal and at least one overbasing agent. The detergent includes less than 6.0% by combined mass of unsulphurized C 9 -C 15  alkyl phenol and its unsulphurized metal salt. The lubricating oil composition exhibits an improved rate of acid neutralization.

The present invention is concerned with a lubricating oil compositionsuitable for use as a marine diesel cylinder lubricant. In particular,the present invention is concerned with a marine diesel cylinderlubricant that exhibits an increased rate of acid neutralization.

Fuels used in marine diesel engines generally include a high sulphurcontent, such as, for example, 2-3%. The exhaust gases therefore includesulphur oxides which react with moisture to form sulphuric acid whichcorrodes and wears components in the diesel engine, such as cylinderliners and piston rings. Therefore, any acid must be neutralized asquickly as possible.

EP 0 839 894A discloses a marine diesel cylinder lubricant that exhibitsa rapid neutralization rate. The lubricant includes (A) at least onecompound selected from the group consisting of overbased sulphonates,phenates or salicylates of alkaline earth metals, and (B) a bis-typesuccinic imide compound having an absorption ratio, α/β, of absorptionpeaks in an IR spectrum of not more than 0.005, wherein α is theintensity of an absorption peak at 1550±10 cm⁻¹ and β is the intensityof absorption peak at 1700±cm⁻¹.

EP 1 051 467B also discloses a marine diesel cylinder lubricant thatexhibits a rapid neutralization rate. The lubricant includes 0.5 to 2.5%by weight of a succinimide dispersant, 3.5 to 10% by weight of anoverbased sulphonate detergent and 11 to 24.5% by weight of an overbasedphenate detergent.

The aim of the present invention is to provide a lubricant compositionthat exhibits an increased rate of acid neutralization.

FIG. 1 shows graphically the results of Examples 1 through 3,representative of the present invention, and Comparative Example 4.

In accordance with the present invention there is provided a lubricatingoil composition including at least one sulphurized overbased metalphenate detergent prepared from a C₉-C₁₅ alkyl phenol, at least onesulphurizing agent, at least one metal and at least one overbasingagent; the detergent including less than 6.0% by combined mass ofunsulphurized C₉-C₁₅ alkyl phenol and its unsulphurized metal salt.

The lubricating oil composition preferably has a total base number(‘TBN’) of more than 30, preferably more than 35, mgKOH/g, as determinedby ASTM D2896. The lubricating oil composition preferably has a TBN ofless than 100 mgKOH/g, as determined by ASTM D2896.

In accordance with the present invention there is also provided use toincrease the rate of acid neutralization of a lubricating oilcomposition of at least one sulphurized overbased metal phenatedetergent prepared from a C₉-C₁₅ alkyl phenol, at least one sulphurizingagent, at least one metal and at least one overbasing agent; thesulphurized overbased metal phenate detergent including less than 6.0%by mass of unsulphurized C₉-C₁₅ alkyl phenol and its unsulphurized metalsalt.

In accordance with the present invention there is also provided a methodof increasing the rate of acid neutralization of a lubricating oilcomposition, the method including the step of adding to the lubricatingoil composition at least one sulphurized overbased metal phenatedetergent prepared from a C₉-C₁₅ alkyl phenol, at least one sulphurizingagent, at least one metal and at least one overbasing agent; thesulphurized overbased metal phenate detergent including less than 6.0%by mass of unsulphurized C₉-C₁₅ alkyl phenol and its unsulphurized metalsalt.

By ‘alkyl phenol’ we mean phenol having a linear or branched alkyl groupattached thereto.

The metal is preferably calcium.

The overbased phenate detergent is prepared from mono-, di- andpolysulphides of C₉-C₁₅ alkyl phenols. The C₉-C₁₅ alkyl substitutedphenols may contain one or more C₉-C₁₅ alkyl groups per aromatic ring.Preferably, the overbased phenate detergent is prepared from mono-, di-and polysulphides of C₁₀-C₁₃ alkyl phenols.

The sulphurized C₉-C₁₅ alkyl phenols may be represented by the generalformula I:

wherein R represents a C₉-C₁₅ alkyl radical, n is an integer of 0 to 20,y is an integer of 0 to 4 and may be different for each aromatic nucleusand x is an integer of from 1 to 7, typically 1 to 4. The individualgroups represented by R may be the same or different and may containfrom 9 to 15, preferably 10 to 13, carbon atoms. Preferably n is 0 to 4,y is 1 or 2 and may be different for each aromatic nucleus and x is 1 to4.

The sulphurized C₉-C₁₅ alkyl substituted phenols may be mixtures of theabove general formula and may include un-sulphurized phenolic material.It is preferred that the level of un-sulphurized phenolic material iskept to a minimum. The sulphurized C₉-C₁₅ alkyl substituted phenols maycontain up to 15%, preferably up to 9%, by weight of un-sulphurizedphenolic material. One preferred group of sulphur zed C₉-C₁₅ alkylsubstituted phenols are those with a sulphur content of between 4 and 16mass %, preferably 4 to 14%, and most preferably 6 to 12 mass %.

The sulphurized phenols, which will normally comprise a mixture ofdifferent compounds, typically contain at least some sulphur which iseither free, or is only loosely bonded; the sulphur thus being availableto attack nitrile elastomeric seals and is referred to as activesulphur. This active sulphur may be present in the form ofpolysulphides, for example when x is three or greater in formula I; inthis form the active sulphur may be present at levels which aretypically up to 2 wt % or more.

The sulphurized C₉-C₁₅ alkyl phenols are prepared by the reaction ofC₉-C₁₅ alkyl phenols in the presence of a sulphurizing agent; thesulphurizing agent being an agent which introduces S_(X) bridging groupsbetween phenols where x is 1 to 7. Thus the reaction may be conductedwith elemental sulphur or a halide thereof such as sulphur monochlorideor sulphur dichloride. Preferably, sulphur monochloride is used.

The C₉-C₁₅ alkyl substituted phenols may be any phenol of generalformula II

wherein R and y are as defined above. Mixtures of phenols of generalformula II may be used.

It is preferred that the oil soluble sulphurized phenol is derived fromsulphur monochloride and has low levels of chlorine such as less than1000 ppm of chlorine. Preferably the chlorine content is 900 ppm or lesse.g. 800 or less and most preferably 500 ppm or less.

It is preferred that the phenol is a mixture of phenols and as such hasan average molecular weight of between 210 and 310, preferably between230 and 290, and most preferably between 250 and 270. Most preferredmixtures are mixtures of para-substituted monoalkylphenols. It ispreferred that the phenols of general formula II are not hinderedphenols although they may be mixtures of phenols which comprise a minorproportion, such as less than 25 wt % e.g. less than 10 wt %, ofhindered phenol. By ‘hindered phenols’ is meant phenols in which all theortho and para reactive sites are substituted, or sterically hinderedphenols in which, either both ortho positions are substituted or onlyone ortho position and the para position are substituted and, in eithercase, the substituent is a tertiary alkyl group, e.g. t-butyl. It ispreferred that for a given mixture of mono and di-alkyl substitutedphenols, e.g. dodecyl substituted, that the mono-substituted phenol ispresent in at least 80 wt % and preferably in the range 90 to 95 wt %.It is preferred that the mole ratio of phenol to sulphur monochloride is2 or greater and most preferably is 2.2 or greater.

The level of sulphur, the required conversion of phenolic material tokeep the un-sulphurized material to a minimum and the chlorine levelsare linked. It is difficult to keep chlorine levels low whilstincreasing sulphur content and achieving the desired conversion, becausemore chlorine containing starting material, i.e. S₂Cl₂, is usuallyrequired to achieve these targets; the task is to be able to achieve lowchlorine whilst at the same time not having a detrimental effect on theother two factors. It is preferred that the reaction is carried out inthe temperature range of −15 or −10 to 150° C., e.g. 20 to 150° C. andpreferably 60 to 150° C. It is most preferred that the reaction iscarried out at less than 110° C.; the use of reaction temperatures below110° C. with certain phenols results in lower levels of chlorine.Typically the reaction temperature is between 60 and 90° C. Preferablythe sulphur monochloride is added to the reaction mixture at a rate of4×10⁻⁴ to 15⁻⁴ cm³ min⁻¹g⁻¹ phenol. If the reaction mixture is notadequately mixed during this addition the chlorine content may increase.The resultant product preferably has a sulphur content of at least 4%,e.g. between 4 and 16%, more preferably 4 to 14% and most preferably atleast 6%, e.g. 7 to 12%. The process has the advantage of not requiringcomplicated post reaction purification steps in order to reduce thelevels of chlorine in the intermediate product.

Olefins and acetylenic compounds may be used to remove active sulphurfrom the sulphurized C₉-C₁₅ alkyl substituted phenols.

Suitable olefins include mono-olefins, di-olefins, tri-olefins or higherhomologues. By suitable is meant olefins which are capable of reactingwith active sulphur and whose properties are such that the excess ofsuch olefins used may be removed from the reaction mixture withoutresulting in significant decomposition of the sulphurized phenol.Preferred olefins are those with a boiling point of up to 200° C. andmost preferably have a boiling point in the range of 150° C. to 200° C.

The mono-olefins may be unsubstituted aliphatic mono-olefins meaningthat they contain only carbon and hydrogen atoms, or they may besubstituted with one or more heteroatoms and/or heteroatom containinggroups e.g. hydroxyl, amino, cyano. An example of a suitable cyanosubstituted mono-olefin is fumaronitrile. The mono-olefins may also besubstituted with aromatic functionality as, for example, in styrene. Themono-olefins may contain for example ester, amide, carboxylic acid,carboxylate, alkaryl, amidine, sulphinyl, sulphonyl or other suchgroups. It is preferred that the mono-olefins are aliphatic and are notsubstituted with heteroatoms and/or heteroatom containing groups otherthan hydroxyl or carboxylate groups. The mono-olefins may be branched ornon-branched.

The mono-olefin preferably has from 4 to 36 carbon atoms and mostpreferably 8 to 20 carbon atoms. The mono-olefin may, for example, be anα-olefin. Examples of α-olefins which may be used include: 1-butene,1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene,1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene,1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-heneicosene,1-docosene, 1-tetracosene, 1-pentacosene, 1-hexacosene, 1-octacosene,and 1-nonacosene. The α-olefin may be a mixture of α-olefins such as thefollowing commercially available mixtures: C₁₅-C₁₈, C₁₂-C₁₆, C₁₄-C₁₆,C₁₄-C₁₈, C₁₆-C₂₀, C₂₂-C₂₈, and C₃₀₊ (Gulftene available from the GulfOil Company).

Another class of mono-olefins are those containing a saturated alicyclicring and one double bond, e.g. an exocyclic double bond. The alicyclicring preferably contains at least six carbon atoms, and, advantageously,the alicyclic ring is substituted by a methylene bridging group thatforms a four-membered ring with three of the ring carbon atoms. Themethylene carbon atom in such a bridging group may be substituted,preferably by two methyl groups, e.g. as in β-pinene. Other examples ofmono-olefins include α-pinene, methylene cyclohexane, camphene, andmethylene cyclopentane etc. and unsaturated compounds such as thevarious derivatives of acrylic acid such as acrylate, methacrylate andacrylamide derivatives.

An example of a suitable mono-olefin is the C₁₂ tetramer of propylene.Other suitable mono-olefins include oligomers of, for example, ethylene.Typically oligomeric olefins are mixtures; therefore mixtures ofoligomeric mono-olefins may be used such as mixtures of propyleneoligomers.

The di-olefins, tri-olefins and higher homologues may be any sucholefins which meet the above identified performance requirement for theolefin. Preferred di-olefins, tri-olefins and higher homologues arethose selected from:

(a) an acyclic olefin having at least two double bonds adjacent doublebonds being separated by two saturated carbon atoms; or(b) an olefin comprising an alicyclic ring, which ring comprises atleast eight carbon atoms and at least two double bonds, each double bondbeing separated from the closest adjacent double bond(s) by twosaturated carbon atoms.

The preferred olefins of group (a) are unsubstituted or substitutedlinear terpenes. Unsubstituted linear terpenes for use in accordancewith the invention may be represented by the formula (C₅H₈)_(n) whereinn is at least 2, that is, a terpene containing carbon and hydrogen atomsonly. An example of an unsubstituted linear terpene is squalene (inwhich n in the above formula is 6). Possible substituents for linearterpenes to be used are, for example, hydroxyl groups. Suitablesubstituted terpenes include farnasol and geraniol with geraniol beingpreferred. Other examples of suitable di-olefins includedicyclopentadiene, dipentene, 1,3-cyclohexadiene, 1,5,-cyclooctadiene,methylcyclopentadiene, limonene and 1,4-cyclohexadiene and polybutadieneetc.

If desired, the group (b) olefins may contain at least three doublebonds, each end of each double bond being separated from each adjacentdouble bond by two saturated carbon atoms. An example of a suitablegroup (b) olefin having three double bonds is 1,5,9-cyclododecatriene.An example of another tri-olefin is cycloheptatriene.

The acetylenic compounds are compounds which are capable of reactingwith active sulphur and whose properties are such that the excess ofsuch compounds may be removed from the reaction mixture withoutresulting in significant decomposition of the sulphurized phenol. Anexample of a suitable acetylene material is phenyl acetylene.

Olefins are preferred to acetylenic compounds,

More than one olefin may of course be used if desired. Where two or moreolefins are used, these need not be compounds from the same group. Thus,for example, mixtures of mono and diolefins may be used although this isnot preferred.

The olefin or acetylenic compound and active sulphur-containingsulphurized phenol may be added in any order. Thus, for example, theolefin or acetylenic compound may be introduced into a vessel alreadycontaining the sulphurized phenol or vice versa, or the two materialsmay be introduced simultaneously into the vessel. This process may becarried out in a suitable solvent for the reactants and/or products.This is a solvent which does not cause problems in removal which effectstability of the product. An example of a suitable solvent which may beused is SN150 basestock. In some instances the olefin when used in asufficient amount may act as a solvent for the reaction.

The mass ratio of sulphurized phenol to olefin or acetylenic compound issuch that the olefin or acetylenic compound is always in excess of thatrequired to react with the active sulphur present in the intermediate.The exact levels will depend on the nature of the olefin or acetyleniccompound, i.e. whether or not, for example, it is a mono, di or triolefin, its molecular weight and the molecular weight of the sulphurizedphenol used, its level of sulphur and level of active sulphur. Forexample, when the olefin is C₁₂ propylene tetramer the ratio ispreferably in the range 1.3:1 to 9:1.

It is preferred that the reaction between the sulphurized phenol and theolefin or acetylenic compound is carried out at an elevated temperatureof greater that 120° C. and, most preferably between 120° C. to 250° C.,and for 0.5 to 60 hours.

Substantially all of the unreacted olefin or acetylenic compound shouldbe removed preferably by means of vacuum distillation, post reaction, orother separation methods. The exact method used will depend on thenature of the olefin or acetylenic compound used. In some circumstancesthe unreacted olefin or acetylenic compound may be removed by simplyapplying a vacuum to the reaction vessel or may require the use ofapplied heating to elevate the temperature of the reaction mixture.Preferably the unreacted material is removed by means of vacuumdistillation and where necessary with the use of heating. Othermaterial, such as volatile material when vacuum distillation is used,may be removed at the same time as the unreacted olefin or acetyleniccompound. By ‘substantially all the unreacted olefin or acetyleniccompound’ is meant that proportion which may be removed by the use ofsuch techniques as, for example, vacuum distillation. Typically therewill be less than 3 wt % of unreacted olefin or acetylenic compoundremaining in the product and preferably between 0 to 3 wt % and mostpreferably 0.5 wt % or less. This residual material may comprise as amajor proportion the higher molecular weight fractions present in theoriginal olefin composition or mixture used. For example, in the case ofthe olefin being a propylene tetramer, which is typically a mixture ofolefins, residual material after removal of excess olefin may comprise ahigh proportion of, for example, pentamer and higher homologues ofpropylene.

It has been found that removal of substantially all the unreacted olefinor acetylenic compound is required so that lubricating oil compositionscomprising olefin or acetylenic compound reacted additives achieveacceptable performance in the Panel Coker test. This is an industrystandard bench test which is used to screen additives in lubricating oilformulations to evaluate their efficacy as, for example, antioxidantsand/or their ability to prevent deposition of carbonaceous deposits bymaintaining such deposits in a dispersed form in the oil. If the excessolefin or acetylenic compound is not removed inferior Panel Cokerperformance of the oil is observed. This is a particular problem withdi-olefins.

On completion of the reaction between sulphur monochloride and thephenol, the temperature of the reaction mixture is increased to theolefin or acetylenic compound reaction temperature and the reactioncarried out. This increase in temperature may be achieved by means of aramped temperature increase to the reaction temperature. The olefin oracetylenic compound may be added to the intermediate reaction mixturebefore, during or after the temperature increase.

A catalyst may be used for the reaction between the olefin or acetyleniccompound and the sulphurized phenol. Suitable catalysts includesulphurisation catalysts and nitrogen bases. The preferred catalysts arenitrogen bases. Suitable nitrogen bases include nitrogen-containingashless dispersants which are commercially available materials such asMannich bases and the reaction products of hydrocarbyl acylating agentswith amines, in particular polyisobutenyl succinimides may be used;these may be prepared by any of the conventional routes. It is preferredto use a polyisobutenyl succinimide in which the polyisobutenyl succinicanhydride is prepared using the so-called thermal process in whichpolyisobutene is reacted directly with maleic anhydride, without the useof chlorine, before reaction with the amine to produce the finaldispersant. Other suitable nitrogen bases include simple amines such as,for example, mono-, di-, and tri-butylamines, polyamines such as, forexample, diethylenetriamine (DETA), triethylenetetramine (TETA) andtetraethylenepentamine (TEPA), cyclic amines for example morpholines andaromatic amines such as commercial diphenylamines. A particularlysuitable amine is n-octylamine. It has also surprisingly been found thatnitrile seal compatibility improves with the use of increasing levels ofcatalyst to prepare the additives of the present invention.

The reaction with olefin or acetylenic compound has the benefit ofreducing the level of chlorine in sulphurized compounds.

The sulphurized C₉-C₁₅ alkyl substituted phenols are used to prepare theoverbased metal phenates by reaction with alkali or alkaline earth metalsalts or compounds. The overbased metal phenates may also have lowlevels of chlorine e.g. less than 1000 ppm. The overbased metal phenatescomprise neutralized detergent as the outer layer of a metal base (e.g.carbonate) micelle. Such overbased metal phenates may have a TBN (totalbase number as determined by ASTM D 2896) of 50 or greater, preferably100 or greater, more preferably 150 or greater, and typically of from250 to 450 or more. The metals are in particular the alkali or alkalineearth metals, e.g., sodium potassium, lithium, calcium, and magnesium.The most commonly used metals are calcium and magnesium and mixtures ofcalcium and/or magnesium with sodium.

The overbased phenates may include at least one further surfactant suchas, for example, a sulphonic acid or an aliphatic carboxylic acid suchas, for example, stearic acid.

Sulphonic acids are typically obtained by sulphonation ofhydrocarbyl-substituted, especially alkyl-substituted, aromatichydrocarbons, for example, those obtained from the fractionation ofpetroleum by distillation and/or extraction, or by the alkylation ofaromatic hydrocarbons. Examples include those obtained by alkylatingbenzene, toluene, xylene, naphthalene, biphenyl or their halogenderivatives, for example, chlorobenzene, chlorotoluene orchloronaphthalene. Alkylation of aromatic hydrocarbons may be carriedout in the presence of a catalyst with alkylating agents having fromabout 3 to more than 100 carbon atoms, such as, for example,haloparaffins, olefins that may be obtained by dehydrogenation ofparaffins, and polyolefins, for example, polymers of ethylene,propylene, and/or butene. The alkylaryl sulphonic acids usually containfrom about 7 to about 100 or more carbon atoms. They preferably containfrom about 16 to about 80 carbon atoms, or 12 to 40 carbon atoms, peralkyl-substituted aromatic moiety, depending on the source from whichthey are obtained.

Another type of sulphonic acid which may be used comprises alkyl phenolsulphonic acids. Such sulphonic acids can be sulphurized. Whethersulphurized or non-sulphurized these sulphonic acids are believed tohave surfactant properties comparable to those of sulphonic acids,rather than surfactant properties comparable to those of phenols.

Sulphonic acids suitable for use also include alkyl sulphonic acids. Insuch compounds the alkyl group suitably contains 9 to 100 carbon atoms,advantageously 12 to 80 carbon atoms, especially 16 to 60 carbon atoms.Carboxylic acids which may be used include mono- and dicarboxylic acids.Preferred monocarboxylic acids are those containing 1 to 30 carbonatoms, especially 8 to 24 carbon atoms. Examples of monocarboxylic acidsare iso-octanoic acid, stearic acid, oleic acid, palmitic acid andbehenic acid. Iso-octanoic acid may, if desired, be used in the form ofthe mixture of C₈ acid isomers sold by Exxon Chemical under the tradename “Cekanoic”, Other suitable acids are those with tertiarysubstitution at the α-carbon atom and dicarboxylic acids with more than2 carbon atoms separating the carboxylic groups. Further, dicarboxylicacids with more than 35 carbon atoms, for example, 36 to 100 carbonatoms, are also suitable. Unsaturated carboxylic acids can besulphurized.

In another aspect of the invention, the carboxylic acid/derivative, ifused, has 8 to 11 carbon atoms in the carboxylic-containing moiety.

In a further aspect of the invention, where a carboxylic acid/derivativeis used, this is not a monocarboxylic acid/derivative with more than 11carbon atoms in the carboxylic-containing moiety. In another aspect, thecarboxylic acid/derivative is not a dicarboxylic acid/derivative withmore than 11 carbon atoms in the carboxylic-containing moiety. In afurther aspect, the carboxylic acid/derivative is not a polycarboxylicacid/derivative with more than 11 carbon atoms in thecarboxylic-containing moiety. In another aspect, a carboxylic acidsurfactant is not a hydrocarbyl-substituted succinic acid or aderivative thereof.

Examples of other surfactants which may be used include the followingcompounds, and derivatives thereof: naphthenic acids, especiallynaphthenic acids containing one or more alkyl groups, dialkylphosphonicacids, dialkylthiophosphonic acids, and dialkyldithiophosphoric acids,high molecular weight (preferably ethoxylated) alcohols, dithiocarbamicacids, thiophosphines, and dispersants, Surfactants of these types arewell known to those skilled in the art.

Metal salts of sulphurized phenols are prepared by reaction with anappropriate metal compound such as an oxide or hydroxide and neutral oroverbased products may be obtained by methods well known in the art.

Examples of suitable overbasing agents are carbon dioxide, a source ofboron, for example, boric acid, sulphur dioxide, hydrogen sulphide, andammonia. Preferred overbasing agents are carbon dioxide or boric acid,or a mixture of the two. The most preferred overbasing agent is carbondioxide and, for convenience, the treatment with an overbasing agentwill in general be referred to as “carbonation”. Unless the contextclearly requires otherwise, it will be understood that references hereinto carbonation include references to treatment with other overbasingagents.

Advantageously, on completion of the carbonation step, part of the basiccalcium compound remains uncarbonated. Advantageously, up to 15 mass %of the basic calcium compound remains uncarbonated, especially up to 11mass %.

Carbonation is effected at less than 100° C. Typically the carbonationis effected at least 15° C., preferably at least 25° C. Advantageously,carbonation is carried out at less than 80° C., more advantageously lessthan 60° C. preferably at most 50° C., more preferably at most 40° C.,and especially at most 35° C. Advantageously, the temperature ismaintained substantially constant during the, or each, carbonation step,with only minor fluctuations. Where there is more than one carbonationstep, both or all carbonation steps are preferably carried out atsubstantially the same temperature, although different temperatures maybe used, if desired, provided that each step is carried out at less than100° C.

Carbonation may be effected at atmospheric, super-atmospheric orsub-atmospheric pressures. Preferably, carbonation is carried out atatmospheric pressure.

Advantageously, there is a first carbonation step that is followed by a“heat-soaking” step in which the mixture is maintained, without additionof any further chemical reagents, in a selected temperature range (or ata selected temperature), which is normally higher than the temperatureat which carbonation is effected, for a period before any furtherprocessing steps are carried out. The mixture is normally stirred duringheat-soaking. Typically, heat-soaking may be carried out for a period ofat least 30 minutes, advantageously at least 45 minutes, preferably atleast 60 minutes, especially at least 90 minutes. Temperatures at whichheat-soaking may be carried out are typically in the range of from 15°C. to just below the reflux temperature of the reaction mixture,preferably 25° C. to 60° C.: the temperature should be such thatsubstantially no materials (for example, solvents) are removed from thesystem during the heat-soaking step. We have found that heat-soaking hasthe effect of assisting product stabilization, dissolution of solids,and filterability.

Preferably, following the first carbonation step (and the heat-soakingstep, if used), a further quantity of basic calcium compound is added tothe mixture and the mixture is again carbonated, the second carbonationstep advantageously being followed by a heat-soaking step.

Basic calcium compounds for use in manufacture of the overbaseddetergents include calcium: oxide, hydroxide, alkoxides, andcarboxylates. Calcium oxide and, more especially, hydroxide arepreferably used. A mixture of basic compounds may be used, if desired.

The mixture to be overbased by the overbasing agents should normallycontain water, and may also contain one or more solvents, promoters orother substances commonly used in overbasing processes.

Examples of suitable solvents are aromatic solvents, for example,benzene, alkyl-substituted benzenes, for example, toluene or xylene,halogen-substituted benzenes, and lower alcohols (with up to 8 carbonatoms). Preferred solvents are toluene and methanol. The amount oftoluene used is advantageously such that the percentage by mass oftoluene, based on the calcium overbased detergent (excluding oil) is atleast 1.5, preferably at least 15, more preferably at least 45,especially at least 60, more especially at least 90. Forpractical/economic reasons, the said percentage of toluene is typicallyat most 1200, advantageously at most 600, preferably at most 500,especially at most 150. The amount of methanol used is advantageouslysuch that the percentage by mass of methanol, based on the calciumdetergent (excluding oil) is at least 1.5, preferably at least 15, morepreferably at least 30, especially at least 45, more especially at least50. For practical/economic reasons, the said percentage of methanol (assolvent) is typically at most 800, advantageously at most 400,preferably at most 200, especially at most 100. The above percentagesapply whether the toluene and methanol are used together or separately.

Examples of suitable promoters are lower alcohols (with up to 8 carbonatoms) and water. Preferred promoters for use in accordance with theinvention are methanol and water. The amount of methanol used isadvantageously such that the percentage by mass of methanol, based onthe initial charge of basic calcium compound, for example, calciumhydroxide (that is, excluding any basic calcium compound added in asecond or subsequent step) is at least 6, preferably at least 60, morepreferably at least 120, especially at least 180, more especially atleast 210. For practical/economic reasons, the said percentage ofmethanol (as promoter) is typically at most 3200, advantageously at most1600, preferably at most 800, especially at most 400. The amount ofwater in the initial reaction mixture (prior to treatment with theoverbasing agent) is advantageously such that the percentage by mass ofwater, based on the initial charge of basic calcium compound(s), forexample, calcium hydroxide, (that is, excluding any basic calciumcompound(s) added in a second or subsequent step) is at least 0.1,preferably at least 1, more preferably at least 3, especially at least6, more especially at least 12, particularly at least 20. Forpractical/economic reasons, the said percentage of water is typically atmost 320, advantageously at most 160, preferably at most 80, especiallyat most 40. If reactants used are not anhydrous, the proportion of waterin the reaction mixture should take account of any water in thecomponents and also water formed by neutralization of the surfactants.In particular, allowance must be made for any water present in thesurfactants themselves.

Advantageously, the reaction medium comprises methanol, water (at leastpart of which may be generated during salt formation), and toluene.

If desired, low molecular weight carboxylic acids (with 1 to about 7carbon atoms), for example, formic acid, inorganic halides, or ammoniumcompounds may be used to facilitate carbonation, to improvefilterability, or as viscosity agents for overbased detergents. Theprocess does not, however, require the use of an inorganic halide orammonium salt catalyst, for example, ammonium salts of lower carboxylicacids or of alcohols, and the overbased detergents produced are thuspreferably free from groups derived from such a halide or ammoniumcatalyst. (Where an inorganic halide or ammonium salt is used in anoverbasing process the catalyst will normally be present in the finaloverbased detergent.)

Oil-soluble, dissolvable, or stably dispersible as that terminology isused herein does not necessarily indicate that the additives orintermediates are soluble, dissolvable, miscible, or capable of beingsuspended in oil in all proportions. It does mean, however, that theyare, for instance, soluble or stably dispersible in oil to an extentsufficient to exert their intended effect in the environment in whichthe oil is employed. Moreover, the additional incorporation of otheradditives may also permit incorporation of higher levels of a particularadditive or intermediate, if desired.

The overbased phenates can be incorporated into base oil in anyconvenient way. Thus, they can be added directly to the oil bydispersing or by dissolving them in the oil at the desired level ofconcentration, optionally with the aid of a suitable solvent such as,for example, toluene, cyclohexane, or tetrahydrofuran. In some casesblending may be effected at room temperature: in other cases elevatedtemperatures are advantageous such as up to 100° C.

Base oils include those suitable for use in marine diesel engines.

Synthetic base oils include alkyl esters of dicarboxylic acids,polyglycols and alcohols: poly-α-olefins, polybutenes, alkyl benzenes,organic esters of phosphoric acids and polysilicone oils.

Natural base oils include mineral lubricating oils which may vary widelyas to their crude source, for example, as to whether they areparaffinic, naphthenic, mixed, or paraffinic-naphthenic, as well as tothe method used in their production, for example, distillation range,straight run or cracked, hydrorefined, solvent extracted and the like.

More specifically, natural lubricating oil base stocks which can be usedmay be straight mineral lubricating oil or distillates derived fromparaffinic, naphthenic, asphaltic, or mixed base crude oils.Alternatively, if desired, various blended oils may be employed as wellas residual oils, particularly those from which asphaltic constituentshave been removed. The oils may be refined by any suitable method, forexample, using acid, alkali, and/or clay or other agents such, forexample, as aluminium chloride, or they may be extracted oils produced,for example, by solvent extraction with solvents, for example, phenol,sulphur dioxide, furfural, dichlorodiethylether, nitrobenzene, orcrotonaldehyde.

The lubricating oil base stock conveniently has a viscosity of about 2.5to about 12 cSt or mm²/sec and preferably about 3.5 to about 9 cSt ormm²/sec at 100° C.

Additional additives may be incorporated into the lubricating oilcomposition to enable it to meet particular requirements. Examples ofadditives which may be included in lubricating oil compositions arefurther detergents, dispersants, anti-wear agents and pour pointdepressants.

The ashless dispersants comprise an oil soluble polymeric hydrocarbonbackbone having functional groups that are capable of associating withparticles to be dispersed. Typically, the dispersants comprise amine,alcohol, amide, or ester polar moieties attached to the polymer backboneoften via a bridging group. The ashless dispersant may be, for example,selected from oil soluble salts, esters, amino-esters, amides, imides,and oxazolines of long chain hydrocarbon substituted mono anddicarboxylic acids or their anhydrides; thiocarboxylate derivatives oflong chain hydrocarbons; long chain aliphatic hydrocarbons having apolyamine attached directly thereto; and Mannich condensation productsformed by condensing a long chain substituted phenol with formaldehydeand polyalkylene polyamine.

The oil soluble polymeric hydrocarbon backbone is typically an olefinpolymer or polyene, especially polymers comprising a major molar amount(i.e., greater than 50 mole %) of a C₂ to C₁₈ olefin (e.g., ethylene,propylene, butylene, isobutylene, pentene, octene-1, styrene), andtypically a C₂ to C₅ olefin. The oil soluble polymeric hydrocarbonbackbone may be a homopolymer (e.g., polypropylene or polyisobutylene)or a copolymer of two or more of such olefins (e.g., copolymers ofethylene and an alpha-olefin such as propylene or butylene, orcopolymers of two different alpha-olefins). Other copolymers includethose in which a minor molar amount of the copolymer monomers, e.g. 1 to10 mole %, is an α,ω-diene, such as a C₃ to C₂₂ non-conjugated diolefin(e.g. a copolymer of isobutylene and butadiene, or a copolymer ofethylene, propylene and 1,4-hexadiene or 5-ethylidene-2-norbornene).Atactic propylene oligomer typically having Mn of from 700 to 5000 mayalso be used, as described in EP-A-490454, as well as heteropolymerssuch as polyepoxides.

One preferred class of olefin polymers is polybutenes and specificallypolyisobutenes (PIB) or poly-n-butenes, such as may be prepared bypolymerization of a C₄ refinery stream. Other preferred classes ofolefin polymers are ethylene alpha-olefin (EAO) copolymers andalpha-olefin homo- and copolymers having in each case a high degree(e.g. >30%) of terminal vinylidene unsaturation. That is, the polymerhas the following structure:

wherein P is the polymer chain and R is a C₁-C₁₈ alkyl group, typicallymethyl or ethyl. Preferably the polymers will have at least 50% of thepolymer chains with terminal vinylidene unsaturation. EAO copolymers ofthis type preferably contain 1 to 50 wt % ethylene, and more preferably5 to 48 wt % ethylene. Such polymers may contain more than onealpha-olefin and may contain one or more C₃ to C₂₂ diolefins. Alsousable are mixtures of EAO's of varying ethylene content. Differentpolymer types, e.g. EAO and PIB, may also be mixed or blended, as wellas polymers differing in Mn; components derived from these also may bemixed or blended.

Suitable olefin polymers and copolymers may be prepared by variouscatalytic polymerization processes. In one method, hydrocarbon feedstreams, typically C₃-C₅ monomers, are cationically polymerized in thepresence of a Lewis acid catalyst and, optionally, a catalytic promoter,e.g., an organoaluminum catalyst such as ethylaluminum dichloride and anoptional promoter such as HCl. Most commonly, polyisobutylene polymersare derived from Raffinate I refinery feedstreams. Various reactorconfigurations can be utilized, e.g. tubular or stirred tank reactors,as well as fixed bed catalyst systems in addition to homogeneouscatalysts. Such polymerization processes and catalysts are described,e.g., in U.S. Pat. Nos. 4,935,576; 4,952,739; 4,982,045; and UK-A2,001,662.

Conventional Ziegler-Natta polymerization processes may also be employedto provide olefin polymers suitable for use in preparing dispersants andother additives. However, preferred polymers may be prepared bypolymerising the appropriate monomers in the presence of a particulartype of Ziegler-Natta catalyst system comprising at least onemetallocene (e.g., a cyclopentadienyl-transition metal compound) and,preferably, a cocatalyst or an activator, e.g., an alumoxane compound oran ionising ionic activator such as tri (n-butyl) ammonium tetra(pentafluorophenyl) boron.

Metallocene catalysts are, for example, bulky ligand transition metalcompounds of the formula:

[L]_(m)M[A]_(n)

where L is a bulky ligand; A is a leaving group, M is a transition metaland m and n are such that the total ligand valency corresponds to thetransition metal valency. Preferably the catalyst is four co-ordinatesuch that the compound is ionizable to a 1⁺ valency state. The ligands Land A may be bridged to each other, and if two ligands A and/or L arepresent, they may be bridged. The metallocene compound may be a fullsandwich compound having two or more ligands L which may becyclopentadienyl ligands or cyclopentadienyl derived ligands, or theymay be half sandwich compounds having one such ligand L. The ligand maybe mono- or polynuclear or any other ligand capable of η-5 bonding tothe transition metal.

One or more of the ligands may π-bond to the transition metal atom,which may be a Group 4, 5 or 6 transition metal and/or a lanthanide oractinide transition metal, with zirconium, titanium and hafnium beingparticularly preferred.

The ligands may be substituted or unsubstituted, and mono-, di-, tri,tetra- and penta-substitution of the cyclopentadienyl ring is possible.Optionally the substituent(s) may act as one or more bridge between theligands and/or leaving groups and/or transition metal. Such bridgestypically comprise one or more of a carbon, germanium, silicon,phosphorus or nitrogen atom-containing radical, and preferably thebridge places a one atom link between the entities being bridged,although that atom may and often does carry other substituents.

The metallocene may also contain a further displaceable ligand,preferably displaced by a cocatalyst—a leaving group—that is usuallyselected from a wide variety of hydrocarbyl groups and halogens.

Such polymerizations, catalysts, and cocatalysts or activators aredescribed, for example, in U.S. Pat. Nos. 4,530,914; 4,665,208;4,808,561; 4,871,705; 4,897,455; 4,937,299; 4,952,716; 5,017,714;5,055,438; 5,057,475; 5,064,802; 5,096,867; 5,120,867; 5,124,418;5,153,157; 5,198,401; 5,227,440; 5,241,025; EP-A-129,368; 277,003;277,004; 420436; 520,732; WO91/04257; 92/00333; 93/08199 and 93/08221;and 94/07928.

The oil soluble polymeric hydrocarbon backbone will usually have anumber average molecular weight ( Mn) within the range of from 300 to20,000. The Mn of the polymer backbone is preferably within the range of500 to 10,000, more preferably 700 to 5,000, where its use is to preparea component having the primary function of dispersancy. Polymers of bothrelatively low molecular weight (e.g. Mn=500 to 1500) and relativelyhigh molecular weight (e.g. Mn=1500 to 5,000 or greater) are useful tomake dispersants. Particularly useful olefin polymers for use indispersants have Mn within the range of from 1500 to 3000. Where the oiladditive component is also intended to have a viscosity modifyingeffect, it is desirable to use a polymer of higher molecular weight,typically with Mn of from 2,000 to 20,000; and if the component isintended to function primarily as a viscosity modifier then themolecular weight may be even higher, e.g., Mn of from 20,000 up to500,000 or greater. Furthermore, the olefin polymers used to preparedispersants preferably have approximately one double bond per polymerchain, preferably as a terminal double bond.

Polymer molecular weight, specifically Mn, can be determined by variousknown techniques. One convenient method is gel permeation chromatography(GPC), which additionally provides molecular weight distributioninformation (see W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern SizeExclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979).Another useful method, particularly for lower molecular weight polymers,is vapour pressure osmometry (see, e.g., ASTM D3592). The oil solublepolymeric hydrocarbon backbone may be functionalized to incorporate afunctional group into the backbone of the polymer, or as one or moregroups pendant from the polymer backbone. The functional group typicallywill be polar and contain one or more hetero atoms such as P, O, S, N,halogen, or boron. It can be attached to a saturated hydrocarbon part ofthe oil soluble polymeric hydrocarbon backbone via substitutionreactions or to an olefinic portion via addition or cycloadditionreactions. Alternatively, the functional group can be incorporated intothe polymer in conjunction with oxidation or cleavage of the polymerchain end (e.g. as in ozonolysis),

Useful functionalization reactions include: halogenation of the polymerat an olefinic bond and subsequent reaction of the halogenated polymerwith an ethylenically unsaturated functional compound (e.g. maleationwhere the polymer is reacted with maleic acid or anhydride); reaction ofthe polymer with an unsaturated functional compound by the “ene”reaction absent halogenation; reaction of the polymer with at least onephenol group (this permits derivatization in a Mannich base-typecondensation); reaction of the polymer at a point of unsaturation withcarbon monoxide using a Koch-type reaction to introduce a carbonyl groupin an iso or neo position; reaction of the polymer with thefunctionalizing compound by free radical addition using a free radicalcatalyst; reaction with a thiocarboxylic acid derivative; and reactionof the polymer by air oxidation methods, epoxidation, chloroamination,or ozonolysis. It is preferred that the polymer is not halogenated.

The functionalized oil soluble polymeric hydrocarbon backbone is thenfurther derivatized with a nucleophilic reactant such as an amine,amino-alcohol, alcohol, metal compound or mixture thereof to form acorresponding derivative.

Useful amine compounds for derivatizing functionalized polymers compriseat least one amine and can comprise one or more additional amine orother reactive or polar groups. These amines may be hydrocarbyl aminesor may be predominantly hydrocarbyl amines in which the hydrocarbylgroup includes other groups, e.g. hydroxyl groups, alkoxy groups, amidegroups, nitriles, imidazoline groups, and the like. Particularly usefulamine compounds include mono- and polyamines, e.g. polyalkylene andpolyoxyalklene polyamines of about 2 to 60) conveniently 2 to 40 (e.g.,3 to 20), total carbon atoms and about 1 to 12, conveniently 3 to 12,and preferably 3 to 9 nitrogen atoms in the molecule. Mixtures of aminecompounds may advantageously be used such as those prepared by reactionof alkylene dihalide with ammonia. Preferred amines are aliphaticsaturated amines, including, e.g., 1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane; polyethylene amines suchas diethylene triamine; triethylene tetramine; tetraethylene pentamine;and polypropyleneamines such as 1,2-propylene diamine; anddi-(1,2-propylene)triamine.

Other useful amine compounds include: alicyclic diamines such as1,4-di(aminomethyl)cyclohexane, and heterocyclic nitrogen compounds suchas imidazolines. A particularly useful class of amines are the polyamidoand related amido-amines as disclosed in U.S. Pat. Nos. 4,857,217;4,956,107; 4,963,275; and 5,229,022. Also usable istris(hydroxymethyl)amino methane (THAM) as described in U.S. Pat. Nos.4,102,798; 4,113,639; 4,116,876; and UK 989,409. Dendrimers, star-likeamines, and comb-structure amines may also be used. Similarly, one mayuse the condensed amines disclosed in U.S. Pat. No. 5,053,152. Thefunctionalized polymer is reacted with the amine compound according toconventional techniques as described in EP-A 208,560; U.S. Pat. No.4,234,435 and U.S. Pat. No. 5,229,022.

The functionalized oil soluble polymeric hydrocarbon backbones also maybe derivatized with hydroxy compounds such as monohydric and polyhydricalcohols or with aromatic compounds such as phenols and naphthols.Polyhydric alcohols are preferred, e.g. alkylene glycols in which thealkylene radical contains from 2 to 8 carbon atoms. Other usefulpolyhydric alcohols include glycerol, mono-oleate of glycerol,monostearate of glycerol, monomethyl ether of glycerol, pentaerythritol,dipentaerythritol, and mixtures thereof. An ester dispersant may also bederived from unsaturated alcohols such as allyl alcohol, cinnamylalcohol, propargyl alcohol, 1-cyclohexane-3-ol, and oleyl alcohol, Stillother classes of the alcohols capable of yielding ashless dispersantscomprise the ether-alcohols and including, for example, theoxy-alkylene, oxy-arylene. They are exemplified by ether-alcohols havingup to 150 oxy-alkylene radicals in which the alkylene radical containsfrom 1 to 8 carbon atoms. The ester dispersants may be di-esters ofsuccinic acids or acidic esters, i.e. partially esterified succinicacids; as well as partially esterified polyhydric alcohols or phenols,i.e. esters having free alcohols or phenolic hydroxyl radicals. An esterdispersant may be prepared by one of several known methods asillustrated, for example, in U.S. Pat. No. 3,381,022.

A preferred group of ashless dispersants includes those derived frompolyisobutylene substituted with succinic anhydride groups and reactedwith polyethylene amines (e.g. tetraethylene pentamine, pentaethylene(di)pentamine, polyoxypropylene diamine) aminoalcohols such astrismethylolaminomethane and optionally additional reactants such asalcohols and reactive metals, e.g. pentaerythritol, and combinationsthereof). Also useful are dispersants wherein a polyamine is attacheddirectly to the long chain aliphatic hydrocarbon as shown in U.S. Pat.Nos. 3,275,554 and 3,565,804 where a halogen group on a halogenatedhydrocarbon is displaced with various alkylene polyamines.

Another class of ashless dispersants comprises Mannich base condensationproducts. Generally, these are prepared by condensing about one mole ofan alkyl-substituted mono- or polyhydroxy benzene with about 1 to 2.5moles of carbonyl compounds (e.g. formaldehyde and paraformaldehyde) andabout 0.5 to 2 moles polyalkylene polyamine as disclosed, for example,in U.S. Pat. No. 3,442,808. Such Mannich condensation products mayinclude a long chain, high molecular weight hydrocarbon (e.g. Mn of1,500 or greater) on the benzene group or may be reacted with a compoundcontaining such a hydrocarbon, for example, polyalkenyl succinicanhydride, as shown in U.S. Pat. No. 3,442,808.

Examples of functionalized and/or derivatized olefin polymers based onpolymers synthesized using metallocene catalyst systems are described inU.S. Pat. Nos. 5,128,056; 5,151,204; 5,200,103; 5,225,092; 5,266,223;EP-A-440,506; 513,157; 513,211. The functionalization and/orderivatizations and/or post treatments described in the followingpatents may also be adapted to functionalize and/or derivatize thepreferred polymers described above: U.S. Pat. Nos. 3,087,936; 3,254,025;3,275,554; 3,442,808, and 3,565,804.

The dispersant can be further post-treated by a variety of conventionalpost treatments such as boration, as generally taught in U.S. Pat. Nos.3,087,936 and 3,254,025. This is readily accomplished by treating anacyl nitrogen-containing dispersant with a boron compound selected fromthe group consisting of boron oxide, boron halides, boron acids andesters of boron acids, in an amount to provide from about 0.1 atomicproportion of boron for each mole of the acylated nitrogen compositionto about 20 atomic proportions of boron for each atomic proportion ofnitrogen of the acylated nitrogen composition. Usefully the dispersantscontain from about 0.05 to 2.0 wt. %, e.g. 0.05 to 0.7 wt. %, boronbased on the total weight of the borated acyl nitrogen compound. Theboron, which appears be in the product as dehydrated boric acid polymers(primarily (HBO₂)₃), is believed to attach to the dispersant imides anddiimides as amine salts, e.g. the metaborate salt of the diimide.Boration is readily carried out by adding from about 0.05 to 4, e.g. 1to 3, wt. % (based on the weight of acyl nitrogen compound) of a boroncompound, preferably boric acid, usually as a slurry, to the acylnitrogen compound and heating with stirring at from 135° to 190° C.,e.g. 140°-170° C., for from 1 to 5 hours followed by nitrogen stripping.Alternatively, the boron treatment can be carried out by adding boricacid to a hot reaction mixture of the dicarboxylic acid material andamine while removing water.

Metal-containing or ash-forming detergents function both as detergentsto reduce or remove deposits and as acid neutralisers or rustinhibitors, thereby reducing wear and corrosion and extending enginelife. Detergents generally comprise a polar head with a long hydrophobictail, with the polar head comprising a metal salt of an acidic organiccompound. The salts may contain a substantially stoichiometric amount ofthe metal in which case they are usually described as normal or neutralsalts, and would typically have a total base number or TBN (as may bemeasured by ASTM D2896) of from 0 to 80. It is possible to include largeamounts of a metal base by reacting an excess of a metal compound suchas an oxide or hydroxide with an acidic gas such as carbon dioxide. Theresulting overbased detergent comprises neutralized detergent as theouter layer of a metal base (e.g. carbonate) micelle. Such overbaseddetergents may have a TBN of 150 or greater, and typically of from 250to 450 or more.

Detergents that may be used include oil-soluble neutral and overbasedsulphonates, phenates, sulphurized phenates, thiophosphonates,salicylates, and naphthenates and other oil-soluble carboxylates of ametal, particularly the alkali or alkaline earth metals, e.g., sodium,potassium, lithium, calcium, and magnesium. The most commonly usedmetals are calcium and magnesium, which may both be present indetergents used in a lubricant, and mixtures of calcium and/or magnesiumwith sodium. Particularly convenient metal detergents are neutral andoverbased calcium sulphonates having TBN of from 20 to 450 TBN, andneutral and overbased calcium phenates and sulphurized phenates havingTBN of from 50 to 450.

Dihydrocarbyl dithiophosphate metal salts are frequently used asanti-wear and antioxidant agents. The metal may be an alkali or alkalineearth metal, or aluminium, lead, tin, molybdenum, manganese, nickel orcopper. The zinc salts are most commonly used in lubricating oil inamounts of 0.1 to 10, preferably 0.2 to 2 wt. %, based upon the totalweight of the lubricating oil composition. They may be prepared inaccordance with known techniques by first forming a dihydrocarbyldithiophosphoric acid (DDPA), usually by reaction of one or more alcoholor a phenol with P₂S₅ and then neutralising the formed DDPA with a zinccompound. The zinc dihydrocarbyl dithiophosphates can be made from mixedDDPA which in turn may be made from mixed alcohols. Alternatively,multiple zinc dihydrocarbyl dithiophosphates can be made andsubsequently mixed.

Thus the dithiophosphoric acid containing secondary hydrocarbyl groupsused in this invention may be made by reacting mixtures of primary andsecondary alcohols. Alternatively, multiple dithiophosphoric acids canbe prepared where the hydrocarbyl groups on one are entirely secondaryin character and the hydrocarbyl groups on the others are entirelyprimary in character. To make the zinc salt any basic or neutral zinccompound could be used but the oxides, hydroxides and carbonates aremost generally employed. Commercial additives frequently contain anexcess of zinc due to use of an excess of the basic zinc compound in theneutralisation reaction.

The preferred zinc dihydrocarbyl dithiophosphates useful in the presentinvention are oil soluble salts of dihydrocarbyl dithiophosphoric acidsand may be represented by the following formula:

wherein R and R′ may be the same or different hydrocarbyl radicalscontaining from 1 to 18, preferably 2 to 12, carbon atoms and includingradicals such as alkyl, alkenyl, aryl, arylalkyl, alkaryl andcycloaliphatic radicals. Particularly preferred as R and R′ groups arealkyl groups of 2 to 8 carbon atoms. Thus, the radicals may, forexample, be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl,amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl,2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl,propenyl, butenyl. In order to obtain oil solubility, the total numberof carbon atoms (i.e. R and R′) in the dithiophosphoric acid willgenerally be about 5 or greater. The zinc dihydrocarbyl dithiophosphatecan therefore comprise zinc dialkyl dithiophosphates. At least 50 (mole)% of the alcohols used to introduce hydrocarbyl groups into thedithiophosphoric acids are secondary alcohols.

Additional additives are typically incorporated into the compositions ofthe present invention. Examples of such additives are antioxidants,anti-wear agents, friction modifiers, rust inhibitors, anti-foamingagents, demulsifiers, and pour point depressants.

Pour point depressants, otherwise known as lube oil flow improvers,lower the minimum temperature at which the fluid will flow or can bepoured. Such additives are well known. Typical of those additives whichimprove the low temperature fluidity of the fluid are C₈ to C₁₈ dialkylfumarate/vinyl aceteate copolymers and polyalkylmethacrylates.

Foam control can be provided by many compounds including antifoamant ofthe polysiloxane type, for example, silicone oil or polydimethylsiloxane.

When lubricating compositions contain one or more of the above-mentionedadditives, each additive is typically blended into the base oil in anamount which enables the additive to provide its desired function.Representative effective amounts of such additives, when used in amarine diesel lubricant are as follows:

Mass % a.i.* Mass % a.i.* Additive (Broad) (Preferred) Detergent(s) 1-18  3-12 Dispersant(s) 0.5-5   1-3 Anti-wear agent(s) 0.1-1.5 0.5-1.3Pour point depressant 0.03-0.15 0.05-0.1  Mineral or synthetic base oilBalance Balance *Mass % active ingredient based on the final oil.

The components may be incorporated into a base oil in any convenientway. Thus, each of the components can be added directly to the oil bydispersing or dissolving it in the oil at the desired level ofconcentration. Such blending may occur at ambient temperature or at anelevated temperature.

Preferably all the additives except for the pour point depressant areblended into a concentrate or additive package that is subsequentlyblended into basestock to make finished lubricant. Use of suchconcentrates is conventional. The concentrate will typically beformulated to contain the additives in proper amounts to provide thedesired concentration in the final formulation when the concentrate iscombined with a predetermined amount of basestock.

Preferably the concentrate is made in accordance with the methoddescribed in U.S. Pat. No. 4,938,880. That patent describes making apremix of ashless dispersant and metal detergents that is pre-blended ata temperature of at least about 100° C. Thereafter the pre-mix is cooledto at least 85° C. and the additional components are added.

The final formulations may employ from 2 to 30 mass % and preferably 10to 25 mass %, typically about 15 to 23 mass % of the concentrate oradditive package with the remainder being base oil.

The invention will now be described by way of illustration only withreference to the following examples. In the examples, unless otherwisenoted, all treat rates of all additives are reported as mass percentactive ingredient.

Synthesis of Sulphurized Dodecylphenol Charges:

Charge weights (g) to make approx. 1 kg of sulphurized dodecylphenol:

Charge (g) Reactor Dodecylphenol 1102 Measuring cylinder Sulphurmonochloride 275 Caustic trap Sodium hydroxide 800 (50% aqueous) Water800 Reactor addition Dec-1-ene 202

Heating Profile Day 1:

Start Target Dwell Temp. Temp. Ramp Time Time (° C.) (° C.) (min.)(min.) Ambient 60 10 2 60 80 120 90 80 85 30 2 85 110 30 180

Days 2 and 3:

Start Target Dwell Temp. Temp. Ramp Time Time (° C.) (° C.) (min.)(min.) Ambient 110 40 2 110 175 50 Hold

Method Day 1

Sulphur monochloride (SMC) is corrosive and toxic, and therefore thefollowing method of charging was used to minimize the risk of exposure.A charge of SMC, close to the proposed weight, was first poured into a150 ml beaker and from there to a 100 ml measuring cylinder which hadbeen placed on a balance. The exact weight was recorded from which thedodecylphenol (DDP) charge was calculated. The caustic trap was set upat this stage by charging a 3 litre beaker with sodium hydroxidesolution.

The DDP was then weighed into a 1 litre baffled flask. The flask was setup for reflux and heated to 60° C. under a nitrogen blanket using theabove profile. At 60° C. the sulphur monochloride addition was startedvia a peristaltic pump over 4 hours using two 16 gauge flat endedstainless steel needles joined by viton tubing. The weight loss overtime was noted varying the addition rate as necessary. During this time,while the temperature was allowed to follow the programmed ramp givenabove, the stirrer was adjusted to keep the mixture stirring briskly.The mixture thickened during addition; stirring was started at approx.270 rpm and had been increased to 500 rpm by the end of addition.

At the end of addition the stainless needle and septum were removed, anitrogen sparge was placed in the vessel and nitrogen bubbled throughthe mixture at 200 ml min⁻¹. The temperature was ramped to 110° C.following the profile and then the mixture was held at 110° C. for 3hours. The stirrer was turned down to 240 rpm at 110° C. because themixture became much thinner.

Finally the heating was stopped, the funnel to the trap raised out ofthe solution, the mixture air-cooled to below 60° C. (raising the spargeout of the solution at 85° C.) and the nitrogen flow stopped. It wasleft standing overnight.

Day 2:

Nitrogen sparge and stirring were restarted as before. The viscousmixture was heated gently until mechanical stirring could be switchedon. The prep was then heated to 110° C. in 40 minutes. At 110° C. decenewas added (17% of estimated sulphurized DDP) and the mixture was heatedto 175° C. in a further 50 minutes.

The prep was held at 175° C. for up to 6 hours until the required UVratio (see below) was reached and then the heating was switched off butstirring and nitrogen were continued until the prep had cooled below 60°C. The prep was then switched off.

UV ratio: The UV ratio of absorbances at 291:325 nm was measured onsulphurized DDP samples to determine the extent of polysulphidebreakdown from the initial reaction. The peak at 325 nm was expected todiminish during a successful desulphurization to produce a final ratioexceeding 3.0.

Day 3:

The caustic trap was removed and the flask set up for distillation.Nitrogen blanket and stirring were started and the prep heated to 175°C. using the same profile as in Day 2. The mixture was much thinner thaton day 2 due to the decene addition and stirring could be startedimmediately. At 175° C. high vacuum was applied and held for 2 hours. Atthe end of 2 hours the heating was switched off and the prep cooled tobelow 60° C. under vacuum with stirring and nitrogen still on. Oncebelow 60° C. the prep was switched off. In the case of A (see Tablebelow) the sulphurized DDP was then used as such. In the case of B (seeTable below) the product obtained was blended with SN 150 oil (14%) at60° C. for 1 hr.

Synthesis of Overbased Phenates EXAMPLES A (PHENATE/STEARATE) AND B(PHENATE/SULPHONATE/STEARATE) Charges:

Mass (g) Example A Example B Reactor Toluene 695 632 Methanol 397 361Water 26 24 Oil, SN 150 30 30 Sulphurized dodecylphenol 622 Sulphurizeddodecylphenol 457 Alkylbenzene sulphonic acid 0 39 (Mol. Wt. approx.660, active matter 83%) Reactor Additions Calcium hydroxide 212 195Carbon dioxide 65 66 Oil, SN 150 (second oil charge) 144 178 StearicAcid 93 84 Centrifuge addition Toluene (further toluene charge) 1072 431

Heating Profile:

Start Temp Final Temp Ramp Time Dwell Time (° C.) (° C.) (min.) (min.)Ambient 40 10 2 40 28 10 2 28 60 60 2 60 65 15 — 65 70 90 — 70 75 15 —75 110 50 — 110  120 15 Hold

Method:

The toluene, methanol, water and initial oil were weighed into a 2 litrereaction vessel. The vessel was set up for reflux and heated to 40° C.using the above heating profile. The mixture was stirred at 200 rpm.Calcium hydroxide was added at 33° C. At 40° C. stirring was increasedto 400 rpm and the sulphurized dodecylphenol (and alkylbenzene sulphonicacid, if required) were run in over a period of approx. 25 minutes. Theprep was then cooled back to 28° C.

At 28° C. carbonation was started at a rate of approx. 150 ml min−1.Carbonation time was 180 minutes.

Heat soak: after carbonation the mixture was ramped from 28° C. to 60°C. using the above profile. The stearic acid was added at 60° C. at theend of the heat soak. After adding the stearic acid the reaction vesselwas rearranged for distillation and a blanket of nitrogen was applied.The mixture was stripped according to the above profile. The second oilcharge was added at 120° C.

Centrifugation: The product was decanted into a 3 litre beaker andweighed. A further toluene charge was added to the beaker and stirred.The mixture was transferred into centrifuge cans and spun in acentrifuge at 2500 rpm for 30 min. After spinning the mixtures weredecanted to be stripped on a rotary evaporator.

Rotary Evaporator Strip: The oil bath was pre-heated to 160° C. and wasmaintained at this temperature ±10° C. An empty 2 litre pear shapedflask was placed on the rotovap, spun briskly and a vacuum of approx.400 mbar was applied. The supernatant liquid was then bled in slowlyover approx. 40 min. and the solvent allowed to flash off. After all themixture had been added the vacuum was increased to full vacuum andmaintained for 1 hour. After 1 hour the vacuum was released and theproduct was cooled.

The overbased detergent produced had the following characteristics:

Comparative Example- Example A Example B OLOA 219* TBN 258 258 250Unsulphurized 5.58 3.84 6.15 alkyl phenol and its unsulphurized calciumsalt, mass % *OLOA 219 is a commercially available 250 BN calciumphenate.

The detergents in the table above were tested for their rates ofneutralization using the following test method:

Acid Neutralisation Rig Method

A 100 ml two neck round bottom flask was fitted with a digital manometer(Digitron model 2083) and an injection port consisting of a glass tapand quick fit adapter. The flask was charged with 30 g of sample (to 0.1mg) and a magnetic stirrer added. The flask was placed in an oil bath at40° C.±1° C. and the sample was allowed to reach equilibrium. 0.182 g of18M sulphuric acid was charged to a syringe and injected into the flaskvia the injection port and the pressure of the CO₂ gas evolved wasrecorded as a function of time. The results are shown in the table belowand also in the attached graph.

The amount of dodecyl phenol (DDP) and its calcium salt was measured asfollows:

Method for Analysis of (Ca) DDP Content

The determination of dodecyl phenol (DDP) and its calcium salt contentwas done by reverse phase HPLC using a u.v. detector. Alkylphenolspecies were differently eluted within ten minutes. The remaining sampleimpurities were washed out from the column with pure methanol A seriesof four calibration standards were prepared by dissolving known amountsof reference DDP in the mobile phase (84% methanol-16% water),concentrations were selected according to the most appropriate range ofdetector response factor and linearity. Analyses of test specimens werecarried out within the calibration range of response. About 0.3 g ofsample solution was dissolved in about 3 g of dichloromethane (ARgrade). The solution was gently agitated. A 20 ml volumetric flask washalf filled with the mobile phase and into this, about 2.6 g of thedichloromethane solution was directly weighed (to nearest 0.1 mg). Thesample was homogenised by agitation or by sonication in a water bath for2 minutes. The flask was diluted to volume with mobile phase and then,by means of a 5 mL plastic syringe and a 0.45 μm disposable celluloseacetate filter, the sample was filtered directly into the HPLC vial. Thesample and calibration solutions were chromotographed using the HPLCconditions below. Integration of the peaks was carried out between 4 and9 minutes, the baseline being flat (the slope being less than 5%) withno drift of the u.v. detector. The reference point for the baseline wastaken at 9 minutes. A linear calibration curve was generated by plottingthe integrated areas of the standards against the amount of DDP used toprepare the standards. This calibration curve was used to determine thecontent of DDP and its calcium salt by combined mass % in the sample.

The HPLC was run with the following conditions:

Column: C8(2) 150 mm×4.6 mm, 5 μm particles size (Luna 100A Phenomexcolumn or equivalent);

Flow rate: 1.2 mL/min;Mobile phase: methanol 84% and water 16%;Typical injection volume: 5 μl;Total run time: 38 min;0-10 min 84% methanol-16% water;10.10-20.00 min 100% methanol (column wash);20.10-38.00 min 84% methanol-16% water;Temperature of the column compartment: 40° C.;UV detector settings: Wavelength: 230 nm (reference at 360 nm for DADsystems).

Comparative Example 1 Example 2 Example 3 Example 4 Example A 8.00 16.00Example B 16.00 OLOA 219 16.00 425 BN 7.10 7.10 7.10 7.10 CalciumSulphonate, Infineum M7117 ExxonMobil 64.90 56.90 56.90 56.90 SN600ExxonMobil 20.00 20.00 20.00 20.00 BS 2500 TBN 50 70 70 70 VK @ 40° C.180.2 196.6 211.8 209.7

Acid Neutralization Testing, CO₂ pressure changes Comparative Time,minutes Example 1 Example 2 Example 3 Example 4 0 0 0 0 0 1 28.0 26.527.0 10.8 2 35.0 29.8 27.8 12.5 3 38.7 32.0 29.2 13.3 4 41.7 34.3 31.013.5 5 45.0 36.0 32.0 13.5 6 47.0 37.0 33.0 13.8 7 49.0 38.3 33.8 13.8 850.3 39.8 35.0 14.0 9 51.7 41.0 35.4 14.3 10 53.2 41.8 35.6 14.3 11 53.742.3 35.8 14.5 12 54.3 42.5 36.2 14.0 13 55.7 42.8 36.4 14.5 14 56.742.5 36.0 14.3 15 57.0 43.5 36.0 14.5 16 56.7 43.8 36.0 14.0 17 57.344.5 36.0 14.0 18 57.7 44.0 35.8 13.8 19 57.7 43.8 35.8 14.0 20 57.743.8 35.8 14.3

The results above show that the use of an overbased sulphurized metalphenate including less than 6.0% by mass of unsulphurized C₉-C₁₅ alkylphenol and its unsulphurized metal salt unexpectedly produces a higherrate of acid neutralization than the use of an overbased sulphurizedmetal phenate including more than 6.0% by mass of unsulphurized C₉-C₁₅alkyl phenol and its unsulphurized metal salt.

1. A lubricating oil composition including at least one sulphurizedoverbased metal phenate detergent prepared from a C₉-C₁₅ alkyl phenol,at least one sulphurizing agent, at least one metal and at least oneoverbasing agent; the detergent including less than 6.0% by combinedmass of unsulphurized C₉-C₁₅ alkyl phenol and unsulphurized metal saltsthereof.
 2. The composition as claimed in claim 1, wherein thesulphurized overbased metal phenate detergent is prepared from a C₁₀-C₁₃alkyl phenol.
 3. The composition as claimed in claim 1, wherein thesulphurized overbased metal phenate detergent also includes at least onefurther surfactant selected from a sulphonic acid or a carboxylic acid.4. The composition as claimed in claim 3, wherein the sulphurizedoverbased metal phenate detergent includes stearic acid as a furthersurfactant.
 5. The composition as claimed in claim 1, wherein thesulphurizing agent is sulphur monochloride.
 6. The composition asclaimed in claim 1, wherein the metal is calcium.
 7. The composition asclaimed in claim 1, wherein the overbased metal phenate detergent hasbeen prepared using a carbonation temperature of less than 100° C.,preferably less than 80° C.
 8. The composition as claimed in claim 7,wherein the overbased metal phenate detergent has been prepared using acarbonation temperature of less than 80° C.
 9. The composition asclaimed in claim 1, wherein the overbasing agent is carbon dioxide. 10.A method of increasing the rate of acid neutralization of a lubricatingoil composition, the method including the step of adding to thelubricating oil composition at least one sulphurized overbased metalphenate detergent prepared from a C₉-C₁₅ alkyl phenol, at least onesulphurizing agent, at least one metal and at least one overbasingagent; the sulphurized overbased metal phenate detergent including lessthan 6.0% by combined mass of unsulphurized C₉-C₁₅ alkyl phenol andunsulphurized metal salts thereof.